Digital communication and storage systems are in widespread use today and have replaced analog communication and storage systems. A vast majority of such systems incorporate encoding techniques to transmit or store information such as audio or video in digital format. These data encoding systems are used for efficient transmission and storage of digitized information. The encoding systems operate in accordance with a particular standard, e.g. MPEG-4. Data bit-rate is a primary constraining factor in the encoding process and every encoding system employs a Rate Controller (RC) which adjusts the operating parameters of the data encoder in accordance with the requirements of the application, the constraints of the standard and achievable bit-rate. The Rate Controller manages the encoding process, within the framework of constrained data bit-rate.
Rate-controllers can be broadly classified as either Constant Bitrate (CBR) controllers or as Variable Bitrate (VBR) controllers. Constant Bitrate (CBR) controllers enable constant-channel-bandwidth operation under variable encoding quality conditions. Variable Bitrate (VBR) controllers, on the other hand, maintain constant encoding quality using variable-channel-bandwidth.
At present, there are various encoding standards and rate control algorithms that are in use. Each rate controller is designed to work within the framework of a particular encoding standard and cannot be used for a different encoding standard.